South Australia and Tasmania are Australia's most obese states

New research data has revealed some alarming figures - including the fact that over 11 million Aussies are now overweight or obese.

Roy Morgan research data has revealed South Australia and Tasmania are Australia's biggest states — not by area but by waist size, with almost three out of 10 people classified as obese.

West Australia and Victoria have the least number of obese residents, with more than three quarters below the national obesity line.

Over 11 million Aussies are now overweight, with the average tipping the scales at 16kg heavier than they should be, according to the research which was released by Medibank.

Experts gathered the data in 12 months to June 2015 and rated obesity levels using body mass index (BMI) levels.

The results showed that 26.2 percent of all Australians return BMIs in the obese category, and 35.1 percent return a BMI in the overweight category.

Despite the need to lose weight, experts are warning against "short-term extreme diets" as part of your New Year's resolution.

"A diet that's too restrictive is usually one that's destined to fail, whereas a balanced diet can be enjoyable and you don't have to give up all of those foods you love," says Dr Kevin Cheng, the head of Integrated Care at Medibank.

Dr Cheng's tips to nail your weight-loss resolution

1. Pay attention to what you're eating

Many people inadvertently gain weight because they eat when distracted, says Dr Cheng.

The best approach is to try and avoid multitasking like sending emails or watching TV when you sit down for meals.

"Slowing down and savouring your food can help you control your intake," says Dr Cheng.

2. Never skip breakfast

It's the meal that breaks your fast, and for people trying to lose weight it's essential you kick start your metabolism first thing in the morning. (The best breakfasts to suit your goal – be it muscle gain or fat loss – can be found here.)

3. Don’t drink your calories

Many people might be eating correctly but consuming excessive calories through what they drink, says Dr Cheng.

"Drinks like soft drinks, milky coffee and alcohol are loaded with sugar and are empty calories. Dehydration can mimic the feeling of hunger and is a major cause of fatigue."

4. Instead of crash exercising, ease yourself into it

Many New Year's resolutioners hit the gym in January with the force of a thousand suns – only to be so sore they never go back.

Dr Cheng recommends easing yourself into any new exercise program, as it’s easy to lose motivation when completing marathon efforts.

"Try walking for 20 to 30 minutes a day and taking advantage of pay-as-you-go gym passes," says Dr Cheng.

5. Be flexible – but not too flexible – with your diet

Any diet that has zero room for a cheeky chocolate bar or six is unlikely to last long, advises Dr Cheng. But while your diet should have some wiggle room, it shouldn’t allow you to binge on junk food often.

"That's not to say a greasy burger and a big bowl of chips should be a regular occurrence, but there's nothing wrong with a square of chocolate or a glass of wine over dinner every now and again," says Dr Cheng.